1. Technical Field
The present invention is related to a display apparatus and its related control method, and more particularly to a RGBW display apparatus and its related control method.
2. Description of the Related Art
It is well-known that a display panel of liquid crystal display (LCD) apparatus generally is configured with a plurality of pixels each having a red color sub-pixel (R sub-pixel), a green color sub-pixel (G sub-pixel), and a blue color sub-pixel (B sub-pixel). The display apparatus composed by R sub-pixels, G sub-pixels and B sub-pixels is termed as a RGB display apparatus. In the RGB display apparatus, the size of each sub-pixel is ⅓ of the size of a single pixel.
With respect to portable display apparatus, high luminance and power saving capability are very important. Accordingly, a RGBW display apparatus which can increase transmittance and reduce backlight power consumption has been proposed. That is, each pixel in a display panel of the RGBW display apparatus is composed by a R sub-pixel, a G sub-pixel, a B sub-pixel and a W sub-pixel. In such RGBW display apparatus, the high transmittance of white sub-pixel is used to increase the luminance of the display apparatus and thereby achieving the effect of power saving.
However, in the display panel of such RGBW display apparatus, the size of each sub-pixel is smaller than the size of each sub-pixel in the conventional RGB display apparatus as described above. As a result, in the situation of the RGBW display apparatus is expected to display pure color or approximate pure color images, the luminance and chromaticity are worse than that of the conventional RGB display apparatus. In other words, because of the addition of the white sub-pixel in each pixel, the luminance and chromaticity are degraded in the use of displaying the pure color and approximate pure color images.
Since three-color image input signals received by the RGBW display apparatus each only includes a red color signal (R signal), a green color signal (G signal) and a blue color signal (B signal), and therefore in order to facilitate the RGBW display apparatus to achieve the display capability of luminance and chromaticity similar to that of the conventional RGB display apparatus, the control circuit in the RGBW display apparatus is necessary to adjust the backlight signal, and the R signal, the G signal and the B signal are needed to be further processed.
Referring to FIG. 1, showing a schematic functional block diagram of a conventional RGBW display apparatus. The RGBW display apparatus 100 includes a four-color mapping unit 110, a dynamic backlight control unit 120, a backlight driving unit 130, a backlight module 140, a source driver 170, a gate driver 180 and a pixel array 190. The pixel array 190 includes a plurality of pixel units 195 each having a data switch Qd, a liquid crystal capacitor Clc and a storage capacitor Cst. The source driver 170 provides a plurality of data signals SD1˜SDm to the pixel array 190. The gate driver 180 provides a plurality of gate signals SG1˜SGn for controlling the pixel units 195 to receive the data signals SD1˜SDn and thereby cooperative with a backlight output intensity provided by the backlight module 140 to display an image on the pixel array 190.
The four-color mapping unit 110 receives three-color image input signals (Ri, Gi, Bi), and a pre-mapping lookup table 111 in the four-color mapping unit 110 is stored with a plurality of mapping scale ratios Ssca. That is, the pre-mapping lookup table 111 outputs the corresponding mapping scale ratios Ssca according to the received three-color image input signals (Ri, Gi, Bi) and thereby generates first set of four-color image signals.
The dynamic backlight control unit 120 receives the mapping scale ratios Ssca, and a scale ratio analyzing unit 121 in the dynamic backlight control unit 120 computes the mapping scale ratios Ssca and thereby outputs an analyzing value Sana according to the statistical computation result. A backlight adjust lookup table 123 in the dynamic backlight control unit 120 provides a backlight adjust signal Sadj to the backlight driving unit 130 according to the analyzing value Sana. A working cycle adjust unit 135 in the backlight driving unit 130 adjusts a pulse width modulation signal Spwm according to the backlight adjust signal Sadj. The backlight module 140 modulates the backlight output intensity according to the pulse width modulation signal Spwm.
Moreover, the dynamic backlight control unit 120 also would produce a mappingss correction signal Scorr to the four-color mapping unit 110. The four-color mapping unit 110 would adjust the first set of four-color image signals to be second set of four-color image signals (R′, G′, B′, W′).
After the source driver 170 receives the second set of four-color image signals (R′, G′, B′, W′), the source driver 170 would generate the data signals SD1˜SDm to the pixel array 190 for image display.
It is found from the above description that the pre-mapping lookup table 111 in the conventional four-color mapping unit 110 needs firstly to map the three-color image input signals (Ri, Gi, Bi) into the first set of four-color image signals, and then adjusts the first set of four-color image signals into the second set of four-color image signals (R′,G′, B′, W′) according to the mapping correction signal Scorr. That is, owing to the mapping correction signal Scorr, all color signals in the first set of four-color image signals would be adjusted to be the second set of four-color image signals (R′, G′, B′, W′), and therefore the pre-mapping lookup table 111 is inevitably to record a large amount of corresponding data and thus the required memory volume is very big, so that the design of the pre-mapping lookup table 111 is very complex.